Method and Cooler for Cooling Hot Particulate Material

ABSTRACT

A method as well as a cooler for cooling hot particulate material which has been subjected to heat treatment in an industrial kiln, such as a rotary kiln for manufacturing cement clinker may be configured such that hot material from the kiln is directed onto a grate in a cooler where cooling gases via at least one cooling gas duct are directed through slots in the grate for cooling the hot material and where compressed air can be injected into the material on the grate. The method as well as the cooler is characterized in that compressed air is injected into the cooling gas duct. The compressed air which is injected into the cooling gas duct may operate as a non-return valve which can ensure that compressed air is injected into the material on the grate and may prevent clinker dust from falling through the cooling gas duct.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States national stage under 35 U.S.C. §371 of International Application No. PCT/EP2009/055887, filed on May 15, 2009, claiming priority to Danish Application No. PA 2008 00879, filed on Jun. 26, 2008. Both of those applications are incorporated by reference herein.

FIELD OF INVENTION

The present invention relates to a method for cooling hot particulate material which has been subjected to heat treatment in an industrial kiln, such as a rotary kiln for manufacturing cement clinker, whereby the hot material from the kiln is directed onto a grate in a cooler where cooling gases via at least one cooling gas duct are led through slots in the grate for cooling the hot material and where compressed air can be injected into the material on the grate. The invention also relates to a cooler for carrying out the method.

BACKGROUND OF THE INVENTION

A cooler of the above mentioned kind is known from EP 1 774 236 where compressed air from a separate system can be intermittently injected into the material on the grate with a view to removing any agglomerates and so-called snowmen formations which are formed by the clogging of clinker material, and causing decreased efficiency of the cooler, and where the duct for cooling gases through the use of an appropriate valve arrangement in the form of for example a tilting damper is blanked off when compressed air is injected. The disadvantage of this known cooler is that the valve arrangement is a mechanically movable component which may wear out relatively quickly when exposed to compressed air in expansion, consequently giving rise to operational problems.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a method as well as a cooler for cooling hot particulate material whereby the aforementioned disadvantage is eliminated.

This is achieved by a cooler of the kind mentioned in the introduction and being characterized in that compressed air is injected into the cooling gas duct.

Embodiments of the method and cooler permit the compressed air which is injected into a cooling gas duct to operate as a non-return valve which will ensure that compressed air is injected into the material on the grate. This is due to the fact that the mass flow inertia and the dynamic pressure of the compressed air being injected into the cooling gas duct will prevent a backflow of the compressed air in the cooling gas duct. The blanking-off of the cooling gas duct thus achieved will further prevent clinker dust from falling through the cooling gas duct.

Preferably, at least a portion of the compressed air which is injected via the cooling gas duct is directed through the slots in the grate and into the material deposited on the grate.

In principle, the compressed air may be injected into the cooling gas duct at any conceivable angle relative to the centerline of the cooling gas duct. Preferably, the compressed air should be injected into the cooling gas duct with a velocity component which is parallel to the centerline of the cooling gas duct and pointing in direction towards the grate, which means that the compressed air must be injected at an angle α of less than 90° relative to the centerline of the cooling gas duct. It is believed that such an injection of compressed air provides the best effect. It is preferred that the compressed air is injected at an angle α of less than 10°, preferably at an angle of 0° relative to the centerline of the cooling gas duct.

In one embodiment of the invention, compressed air may be injected via other pipelines or ducts into the material on the grate while compressed air is simultaneously injected into the cooling gas duct in order to provide the static pressure between the cooling grate and the material which is required for transiently generating an air cushion which will lift the material off the grate, thereby removing snowmen formations and other major material agglomerations from the grate, and leading them downstream through the cooler. However, it is preferred that all compressed air is injected via the cooling gas duct and subsequently directed through the slots in the grate.

The cooler for carrying out the method according to the invention comprises a grate for receiving and supporting hot material from a kiln, at least one cooling gas duct which is connected to slots in the grate for introducing cooling gases into the hot material and a compressed air system for injecting compressed air into the material on the grate and being characterized in that it comprises devices or at least one apparatus configured to inject compressed air into the cooling gas duct.

It is further proposed that the cooler comprises other devices or mechanisms for injecting compressed air into the material on the grate simultaneously with the injection of compressed air into the cooling gas duct.

Other details, objects, and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof and certain present preferred methods of practicing the same proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further details with reference to the drawing, being diagrammatical, and where

FIG. 1 shows a side view of an embodiment of a cooler according to the invention, and

FIGS. 2 and 3 show different embodiments of the cooler according to the invention.

DETAILED DESCRIPTION OF PRESENT PREFERRED EMBODIMENTS

In FIG. 1 a cooler 1 is installed in direct extension of a rotary kiln 3 for manufacturing cement clinker. The cooler comprises an inlet end 4 and an outlet end 5. The cooler 1 also comprises a stationary grate bottom 11 for supporting the cement clinker, a fan 12 for injecting cooling gases up through the clinker via a compartment 13 and not shown in greater detail slots in the inlet grate 11, as well as a number of scraping elements 14 which by means of a not shown driving mechanism can be moved back and forth in the longitudinal direction of the cooler so that the clinker is moved from the inlet end of the cooler to its outlet end.

The cooler 1 also comprises an inlet grate 21 which is located in the inlet end 4 of the cooler immediately under the outlet end of the rotary kiln for receiving the hot cement clinker 2. As may be appreciated by those of at least ordinary skill in the art, the inlet grate may in principle be configured in any appropriate manner. The inlet grate 21 shown as an example is stepped and made up of a number of grate shoes 22. The inlet grate is mounted at a certain inclination relative to the horizontal plane in order to promote the movement of the clinker through the cooler. In the inlet section the cooler also comprises a fan 23 for injecting cooling gas through the clinker via a compartment 24, cooling gas ducts 28 and slots 20 in the inlet grate 22, as well as a separate compressed air system comprising a compressed air tank 25 and a number of pipelines 26 for injecting compressed air into the material on the inlet grate. The pressurized tank 25 may in an alternative embodiment be constituted by a fan.

As illustrated in FIGS. 1 to 3, each pipeline 26 for injecting compressed air into the material on the inlet grate is connected to a cooling gas duct 28, causing the compressed air to be injected into the cooling gas duct, being subsequently passed on to the herewith connected grate shoe 22 and passing through the slots 20 in the grate 21.

As is apparent from FIGS. 2 to 3, the compressed air may be injected into the cooling gas duct 28 at any conceivable angle relative to the centerline of the cooling gas duct 28. Preferably, the compressed air is injected into the cooling gas duct 28 at an angle α of less than 90° relative to the centerline of the cooling gas duct to ensure that the compressed air will have a velocity component which is parallel to the centerline of the cooling gas duct 28 and pointing in the direction towards the grate 21. Such an injection of the compressed air may provide a very desirable effect.

In the embodiment shown in FIG. 3, the compressed air is injected at an angle α of about 30° relative to the centerline of the cooling gas duct 28, whereas the compressed air in the preferred embodiment shown in FIG. 2 is injected parallel to the centerline of the cooling gas duct 28.

During normal operation of the cooler, the compressed air system is closed by means of a valve, such as a solenoid valve. At intervals, the length of which may be predefined or specifically adapted according to the prevailing operating conditions, the compressed air system is opened, causing compressed air to be injected into the cooling gas ducts 28 and directed through the grate shoes 22 towards the clinker bed 2 so that the static pressure between the grate 21 and the clinker bed 2 is increased while transiently generating an air cushion which will lift the material off the grate. Snowmen formations and other major material agglomerations will also be lifted off the inlet grate, subsequently continuing their movement downstream through the cooler. Also it may be desirable to inject compressed air only into selected areas of the inlet grate and, therefore, the cooler may comprise a valve (not shown), such as a solenoid valve, in each compressed air line 26 communicating with the grate.

Compressed air may further via other pipelines or ducts, not shown, be injected into the material on the grate subject to simultaneous injection of compressed air into the cooling gas duct 28 in order to generate the static pressure between the cooling grate 21 and the material bed 2 required to transiently lift the material off the grate.

It should be understood that the compressed air which is injected into the cooling gas duct 28 will operate as a non-return valve which will ensure that compressed air is injected into the material on the grate 21. This is due to the fact that the mass flow inertia and the dynamic pressure of the compressed air being injected into the cooling gas duct 28 will prevent a backflow of the compressed air into the cooling gas duct 28. The blanking-off of the cooling gas duct 28 thus achieved will further prevent clinker dust from falling through the cooling gas duct.

While certain present preferred embodiments of the cooler and certain embodiments of methods of practicing the same have been shown and described, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. 

1. A method for cooling hot particulate material which has been subjected to heat treatment in an industrial kiln for manufacturing cement clinker comprising: directing hot material from the kiln onto a grate in a cooler: passing cooling gases via at least one cooling gas duct through slots in the grate for cooling the hot material and injecting compressed air into the material on the grate; and injecting compressed air into the cooling gas duct.
 2. The method of claim 1 wherein at least a portion of the compressed air which is injected into the cooling gas duct is directed through the slots in the grate and in the material deposited on the grate.
 3. The method of claim 2 wherein the compressed air is injected at an angle α of less than 90° relative to a centerline of the cooling gas duct.
 4. The method of claim 2 wherein the compressed air is injected at an angle α of less than 10° relative to a centerline of the cooling gas duct.
 5. The method of claim 1 wherein the compressed air is injected at an angle α of 0° relative to a centerline centreline of the cooling gas duct.
 6. A cooler for cooling hot particulate material which has been subjected to heat treatment in an industrial kiln for manufacturing cement clinker comprising: a grate for receiving and supporting hot material from the kiln; at least one cooling gas duct that is in communication with slots in the grate for introducing cooling gases to the hot material; and a compressed air system for injecting compressed air into the material on the grate; and wherein the compressed air system is comprised of a compressed air injection mechanism that injects the compressed air into the cooling gas duct.
 7. The cooler of claim 6 wherein the compressed air injected by the compressed air injection mechanism injects the compressed air into the cooling gas duct to operate as a non-return valve such that the compressed air is injected into the material on the grate and also prevents clinker dust from falling through the cooling gas duct.
 8. The cooler of claim 7 wherein the compressed air is injected at an angle α of less than 90° relative to a centerline of the cooling gas duct, the centerline extending along a length of the cooling gas duct.
 9. The cooler of claim 7 wherein the compressed air is injected at an angle α of less than 10° relative to a centerline of the cooling gas duct, the centerline extending along a length of the cooling gas duct.
 10. The cooler of claim 7 wherein the compressed air is injected at an angle α of 0° relative to a centerline of the cooling gas duct, the centerline extending along a length of the cooling gas duct.
 11. The cooler of claim 7 wherein the compressed air injection mechanism is comprised of a valve that is moveable from an on position that injects compressed air to an off position that prevents the compressed air from being injected and wherein the valve is periodically moved from an on position to an off position and periodically moved from the off position to the on position.
 12. The method of claim 6 wherein the compressed air injected into the cooling gas duct is injected periodically into the cooling gas duct.
 13. The method of claim 12 wherein a valve is periodically moved from an on position that injects compressed air into the cooling gas duct to an off position that prevents the compressed air from being injected into the cooling gas duct, and after a predetermined amount of time is then moved from the off position back to the on position. 